Method and apparatus for forming fiber reinforced composite parts

ABSTRACT

A method and apparatus for combining raw fibrous and binding materials in a single mixing step (Step S 3 ), followed by consolidation (Step S 5 ) so as to greatly shorten the overall cycle time to a finished fiber-reinforced composite part. Chopped fibrous materials and binder materials are deposited sequentially onto a belt conveyor (Step S 2 ) so that the materials are successively layered, one on top of each other in a predetermined ratio, and subsequently mixed (Step S 3 ) to achieve uniform dispersion throughout. The mixed materials are then deposited into a rotating mold (Step S 4 ) to further ensure uniform dispersion of fibrous and binder materials. Impregnation of the fibrous materials with the binder material occur in-situ as the uniformly mixed materials are heated and subsequently compacted in the mold (Step S 5 ) to obtain the desired shape of the fiber-reinforced composite part.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method and apparatus forforming fiber reinforced composite parts.

[0003] 2. Description of the Related Art

[0004] Fiber-reinforced composite structures, such as carbon-carboncomposites for example, are widely used as friction materials forheavy-duty brakes in automobiles, trucks, and aircraft. This is becausethey exhibit high thermal conductivity, large heat capacity, andexcellent friction and wear characteristics and thus can provideexcellent performance.

[0005] However, past manufacturing processes for producing thesefiber-reinforced composite structures were often lengthy undertakings,requiring months to fabricate a single part. In one example, a typicalfiber-reinforced composite part was prepared by a non-woven process thatinvolved needle-punching layers of carbon fibers to form a preform, aslow, time-consuming process. When two or more layers of fibers areneedle punched together by metal needles having barbs on one end, thebarbs commingle fibers from a particular layer into successive layers.The commingled fibers essentially stitch the layers of fiber together.This nonwoven technology achieved preform densities on the order ofabout 0.5 g/cc. To obtain a final composite part, the preform wassubsequently infiltrated with a matrix binder material via a chemicalvapor deposition (“CVD”) or chemical vapor infiltration (“CVI”) process,for example. CVD and CVI are used interchangeably for the purposes ofthe present application.

[0006] In another process, a preform was prepared by building upsuccessive layers of pre-impregnated carbon fiber fabric. Tows (the term“tow” is used hereinafter to refer to a strand of continuous filaments)of carbon fiber were woven into a two-dimensional fabric, and thereupondipped into a liquid bath to impregnate the fabric with a liquid resin.The resin-impregnated fabric was then pulled between rollers to form asheet of pre-impregnated carbon-fiber fabric. After impregnation, thefabric was dried and b-staged under low heat. A plurality of desiredshapes were then cut out of the sheet material and stacked within amold, and subsequently cured using heat and pressure to obtain thedesired composite part. In order to produce a carbon-carbon component,the composite part is carbonized which creates internal porosity.Multiple infiltration cycles using CVD or resin were required to achievefinal density of the composite part. For this reason, it often took aterm of several months to obtain a final product, causing the product tobe extremely expensive. Further, much material was wasted in order toobtain the final product.

[0007] Several processes have been developed in order to reduce overallprocessing time needed to manufacture a fiber reinforced composite part.One process, a “random-fiber process”, uses entirely tow material.Somewhat similar to the pre-impregnating method described above, in therandom-fiber process a continuous tow of fiber is dipped through a resinbath, dried, and then chopped to a desired length. The resin coatedchopped fibers are then placed into a mold and cured using heat andpressure. However, the steps of impregnating the continuous tow areperformed separately from the molding and curing required to create thecomposite part, thereby extending the “process cycle” of manufacturingthe composite part.

[0008] Another method involves a molding compound process wherebychopped fibrous material are mixed with a resin so as to form acontinuous sheet of mixed material. A plurality of desired shapes arethen cut out of the sheet material and stacked within a mold, andsubsequently cured using heat and pressure to obtain the desiredcomposite part. Again, this process requires extensive time and wastesmaterial in order to obtain the final product.

[0009] A further process developed to shorten the manufacturing timeinvolves using a liquid slurry to mix the fibrous material with a resinpowder, as illustrated in U.S. Pat. No. 5,744,075 to Klett et al.However, the fibrous material needs to be chopped into small pieces (onthe order of {fraction (1/4)} to {fraction (1/2)} inch (about 0.6-1.3cm)) so as to attain a uniform mix with the resin powder in the slurry.Thus, longer chopped fibers (1-1 ½ inches (about 2.5-3.8 cm)) do notwork well in this liquid slurry method, since a uniform dispersion offibrous material and resin powder in the slurry cannot be attained withthe longer chopped fiber lengths. The longer fibers tended to “ball-up”during mixing with the powdered resin and during deposition into themold, making it difficult to obtain a uniform end product. Moreover,this “balling effect” directly contributed to the “loftiness” of thepreform, a disadvantageous result of the water slurry method since alofty preform was difficult to control within the mold. Additionally, anexcess step of drying the preform was required (i.e., removing the waterfrom the preform in the heating step is required before pressing thematerials into a composite part).

[0010] Recent developments have introduced a method and apparatus thatcombines chopped fibers and a powdered resin utilizing a dry-blendingprocess. Such a dry-blending process and apparatus 100 is illustrated inthe rough schematic diagram of FIG. 1. Apparatus 100 includes a firstlower enclosure 101 connected to a second upper enclosure 102 via a neckportion 119. First enclosure 101 has an adjuster 120 connected theretowhich houses compressed air lines 121 and 124 for feeding air jets 122.Second enclosure 102 houses a screen 126, and has a funnel 132 andvacuum line 135 connected thereto.

[0011] In FIG. 1, chopped tow 115 is loaded into first enclosure 101,where air jets 122 feed compressed air into the chopped tow 115 withinfirst enclosure 101. The compressed air fed via compressed air lines 121and air jets 122 enters below the level of chopped tow in firstenclosure 101. This compressed air forces the chopped tow 115 into upperportion 117 of first enclosure 101 such that the individual fibers ofthe chopped tow 115 are entrained in air and further broken-up(defibrillated) into smaller strands or filaments 118. Adjuster 120maintains the compressed air jets 122 at a level equal to or below thechopped tow 115 within first enclosure 101.

[0012] The broken-up fibers 118 entrained in air in the upper section117 are then forced through neck portion 119 into a second enclosure102, whereby they are mixed with a powdered resin 130 fed through atfunnel 132 of second enclosure 102. The powder resin 130 mixes with thebroken-up fibers in a powder and fiber mixing region 140, whereupon the“mixed materials” settle at the bottom of second enclosure 102 to form alayer which constitutes the building-up of a preform 125. The mixedmaterials fall due to a vacuum 135 being applied to the bottom of secondenclosure 102 which removes the bulk of the air volume in secondenclosure 102, thereby allowing the mixed materials to fall and condenseat the bottom of second enclosure 102 on top of screen 126.

[0013] The “dry-blending” apparatus of FIG. 1 provides a medium formixing the powder 130 with the fibrous material (chopped tow 115) toattain a uniform mixture of the binder material with the fibrousmaterial. However, in the apparatus 100 of FIG. 1, the proportions ofchopped fiber and binder material have to be first individually weighedout to obtain the proper proportions, before being loaded in enclosures101 and 102 to be mixed in mixing region 140. Further, apparatus 100 ofFIG. 1 is limited to a single-batch process, i.e., to make one finalfiber-reinforced composite part, the individual proportions for eachfibrous material and binder material have to be weighed and addedindividually for each preform made.

[0014] Yet a further process to shorten the manufacturing cycle time ofa composite part is illustrated in U.S. Pat. No. 5,236,639 to Sakagamiet al. The objective of this process is to provide excess carbonmaterial to fill pores in the matrix material during subsequent curingand carbonization steps, thus producing a carbon-carbon compositematerial that requires no repetition of production steps including anyfurther densification of the composite material. This involvesmechanically mixing a matrix carbon material and carbon fibers inproportions that are determined on the basis of the carbonization ratioof the matrix material and on the basis of the desired ratio of fibersto be contained in a resultant end product. However, such a processrequires the use of excess carbon matrix material, a curing step underpressure after formation of an intermediate-formed part such as apreform or mold, and also requires subsequent carbonization andgraphitization of the cured intermediate part, both under pressure, toobtain the final fully-densified composite part. Of course, no furtherproduction steps are required or repeated, including densification ofthe composite material. However, it is costly and time consuming toperform the curing, carbonization and graphitization all under pressure.

[0015] Therefore, what is desired is a method and apparatus which wouldfeed, blend, and deposit various lengths of chopped fibrous and bindermaterials into a mold of a desired final shape, wherein the raw fibrousmaterials and binder materials are combined in a single step, followedby consolidation of the materials. The resultant preform would notrequire any curing or carbonization under pressure during the follow-onheating processes to manufacture the final composite part. Such a methodand apparatus would provide fiber-reinforced composite parts withdensities that are higher than achieved with current technologies, andwould decrease overall cycle time to a finished composite part. Themethod can be used to provide an intermediate preform product that issubsequently stabilized, carbonized, optionally heat treated, densified,and final heat treated to provide a carbon-carbon composite material.

SUMMARY OF THE INVENTION

[0016] The present invention provides a method and apparatus forcombining raw fibrous and binding materials in a single mixing step,followed by consolidation so as to greatly shorten the overall cycletime to a finished fiber-reinforced composite part. In the method,chopped fibers, which can include single length or multiple lengths offibrous material, and a powdered resin binder material are combined in acontinuous process at predetermined ratios, mixed together, anddeposited into a mold having the shape of the final product.Specifically, the chopped fibrous materials and binder materials aredeposited sequentially onto a belt conveyor so that the materials aresuccessively layered in a predetermined ratio, and subsequently mixed toachieve uniform dispersion throughout. The “mixed materials” are thendeposited into a rotating mold to further ensure uniform dispersion offibrous and binder materials, wherein impregnation of the fibrousmaterials with the binder material occurs in-situ as the uniformly mixedmaterials are heated in the mold, and subsequently compacted to obtainthe final desired shape of the preform. The resultant preform requiresno excess use of matrix material, no curing or carbonization underpressure in the follow-on heating processes required to obtain theintermediate fiber-reinforced composite part.

[0017] Objectives of the present invention will become more apparentfrom the detailed description given hereinafter. However, it should beunderstood that the detailed description and specific examples, whileindicating preferred embodiments of the invention, are given by way ofillustration only, since various changes and modifications within thespirit and scope of the invention will become apparent to those skilledin the art from this detailed description.

BRIEF DESRIPTION OF THE DRAWINGS

[0018] The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawings,wherein like elements are represented by like reference numerals, whichare given by way of illustration only, and thus are not limitative ofthe present invention and wherein:

[0019]FIG. 1 illustrates a conventional dry-blending apparatus;

[0020]FIG. 2 is a schematic diagram of the equipment and majorcomponents used in accordance with the preferred embodiment of thepresent invention;

[0021]FIG. 3 illustrates a device to rotate the mold in accordance withthe preferred embodiment of the present invention;

[0022]FIG. 4 illustrates general processing steps performed inaccordance with the preferred embodiment of the present invention;

[0023]FIG. 5 illustrates the feeding system in accordance with thepresent invention,

[0024]FIG. 6 illustrates the layer deposition step of FIG. 4 in moredetail;

[0025]FIG. 7 illustrates the mixing step of FIG. 4 in more detail;

[0026]FIG. 8 illustrates the mold deposition step of FIG. 4 in moredetail;

[0027]FIG. 9 illustrates the consolidation step of in more detail; and

[0028]FIG. 10 illustrates the follow-on heating and densification stepof FIG. 4 in more detail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] The method and apparatus in accordance with the preferredembodiment enables the production of fiber-reinforced composite partssuitable for use in manufacturing various components, includingmaterials for high-friction applications such as automobile, truck, andaircraft brakes. By combining fibrous materials with a binder materialin a single apparatus, a fiber-reinforced composite part with improvedfriction and wear performance can be produced in fewer processing stepsas compared to the current techniques of the related art used tofabricate fiber-reinforced composite materials, thereby providingincreased reliability and reduced process cycle times. Additionally, thepreferred embodiment allows for more complete control overdefibrillation of carbon fibers so as to obtain a sufficient balancebetween strength/wear properties with adequate dispersion of mixedcarbon fiber and matrix resin materials, as compared to othermanufacturing processes such as using a liquid slurry, for example.

[0030]FIG. 2 illustrates a schematic diagram of the equipment used inaccordance with the preferred embodiment. Referring to FIG. 2, thefiber-reinforced composite apparatus 200 includes a series of feeders210, 220, and 230, and a constituent transport arrangement, preferably aconveyer belt 205, which is situated below the feeders and adjacentlymounted to a first inlet 241 of a material handling fan 240. An outlet242 of the material handling fan 240 connects to inlet 249 of a cyclonedust collector 260 via line 245. A return air fan 250 takes a suctionoff the cyclone dust collector 260 at point 251. Additionally, thereturn air fan 250 includes an outlet 252 which is connected to a secondinlet 243 of material handling fan 240 via a line 255. The cyclone dustcollector 260 is arranged above a mold 270 that rests on a rotationaldevice 271. Further, fiber-reinforced composite apparatus 200 includes adust filter fan 280 that takes a suction from mold 270 at 275.

[0031] Feeder 210 may feed reinforcing fibers between about 0.5-1.5inches (about 1.3-3.8 cm) in length at a first predetermined rate.Preferably, feeder 210 feeds 1-inch (2.54 cm) fibers (hereinafter“reinforcing fiber”); however, reinforcing fibers longer than 1.5 inches(3.8 cm) may be used. Feeder 220 may feed milled and short fibersbetween about 0.004 inch (0.1 mm) and {fraction (1/2)} inch (1.27 cm) inlength, and preferably feeds 0.004 inch (0.1 mm) length fiber(hereinafter “milled fiber”) at a second predetermined rate. The milledfiber acts as a “filler” fiber to fill in gaps between the longerreinforcing fibers. Feeder 230 can be a resin feeder which feeds a resinbinder material at a third predetermined rate. Alternatively, thefibrous materials from feeders 210 and 220 can be the same size (forexample, equal length fibers up to about 1.5 inches (3.8 cm) in length.It is advantageous to use a mixture of longer and shorter fibers toobtain better friction and wear properties while still maintainingadequate strength in the finished component. The longer fibers providethe strength, while the shorter fibers fill in gaps between the longerfibers and the matrix material to help increase the final density of theintermediate-formed part/preform, and/or of the final composite part.

[0032] The chopped reinforcing and milled fibrous materials can bepolyacrylonitrile (PAN) based carbon fibers, preferably to be used forfabrication of carbon-carbon composite parts. However, glass fibrousmaterial or other reinforcing fibrous material such as metal fibers andsynthetic fibers, for example may be used, depending on the resultantcomposite part to be fabricated. The binder material can be ahigh-carbon yielding mesophase pitch resin matrix (i.e., in powderedform); however, phenolic resins and other thermoplastic or thermosettingresin materials in powdered form may be used as the binder material,depending on the resultant composite part to be fabricated.

[0033] The fibrous chop and resin binder fed from feeders 210, 220, and230 are deposited onto a belt conveyor 205 as a series of continuous,stacked layers. This provides for a semi-continuous process whereby thefeeders contain a sufficient amount of materials to produce manycomposite parts. The stacked layers travel along belt conveyor 205 to bedispensed into a material handling fan 240. Material handling fan 240mixes the fibrous and binder materials, while partially or fullydefibrillating the chopped fiber materials from feeders 210 and 220.Alternatively, the fibrous chop and resin from the feeders may be feddirectly into the material handling fan without a belt conveyer.

[0034] Material handling fan 240 further provides a volume of air flowto convey the “mixed materials” via a line 245 to cyclone dust collector260. The cyclone dust collector 260 receives the air-entrained mixedmaterials and separates the solid particles from the air used to conveythem. Return air fan 250 takes a suction off of cyclone dust collector260 to circulate the bulk of the air volume coming from line 245 back tothe material handling fan 240 via line 255, allowing the remaining mixedmaterials to gently exit the bottom of the cyclone dust collector 260into mold 270. Dust filter fan 280 removes any residual dust created bythe deposition of the mixed materials into the mold 270, and depositsdust particles into dust collector 285. To further ensure uniformdeposition of the mixed materials from cyclone dust collector 260 intomold 270, the mold can be arranged on a rotation device 271.

[0035]FIG. 3 illustrates a rotation device 271 to rotate mold 270 inaccordance with the preferred embodiment of the present invention.Rotation device 271 includes a turntable 272 mounted upon a support 274and connected to an electric motor 276 by a rotating spindle 273.Support 274 (along with turntable 272 and electric motor 276) can bejogged back and forth via air cylinders 277, and rests on a linearactuator 278. The entire assembly is supported by a lift table 279.

[0036] Turntable 272 and the combination of the air cylinders 277 andlinear actuator 278 provide rotational and linear motion for mold 270during the deposition process. In operation, turntable 272 is powered byelectric motor 276 via the spindle 273 to rotate the mold.Simultaneously with this rotation, mold 270 may be reciprocated in a +Xand −X direction for the duration of the deposition process by aircylinders 277, the cylinders essentially jogging the support 274supporting the turntable 272. The mold 270 is aligned to the outlet ofthe cyclone dust collector 260 such that it can be moved up to four (4)inches to either side of the centerline of the cyclone dust collector260 by adjusting linear actuator 278 (for example, the linear actuator“distance” can be set at positions such as −1.0″ (−2.54 cm) or +2.5″(+6.35 cm) from the centerline of the cyclone dust collector 260). Thejogging action imparted by air cylinders 277, together with the rotationimparted by turntable 272, ensures that the mixed material falling fromthe bottom of the cyclone dust collector 260 is uniformly dispersed inthe mold 270 as the mold 270 fills to a desired level, in preparationfor a subsequent consolidation step to be discussed later below.

[0037]FIG. 4 illustrates a process by which fibrous material and bindermaterials are combined to manufacture a fiber-reinforced composite partin accordance with the preferred embodiment. All parameters foroperation are initialized prior to operating the fiber-reinforcedcomposite apparatus 200 (Step S1). This includes determining the ratesat which the fibrous and binder materials will be gravimetrically fedfrom feeders 210, 220, and 230, respectively, onto conveyor belt 205.These rates are determined by a programmable logic controller (PLC) (notdepicted) running a software application, and are based on the desiredratios of these materials in the final formed fiber-reinforced compositepart. Additionally, fan speeds are pre-set for each of the materialhandling fan 240, return fan 250, and dust filter fan 280, andpreferably do not change throughout the entire manufacturing operation.Further, the belt conveyor speed for belt conveyor 205 and the turntablerotational speed and linear actuator distance for rotation device 271are set, and preferably do not change throughout the entiremanufacturing operation.

[0038]FIG. 5 illustrates a feeding system in accordance with the presentinvention. Once the predetermined ratios are set by the operator intoprogrammable logic controller (PLC) 235, the gravimetrical feeding ofthe chopped fiber and resin binder material is controlled by a feedingsystem 290. For example, as illustrated in FIG. 5, the feeding system290 comprises the individual feeders 210, 220 and 230, a common feedercontroller 236 and a set of load cells 211, 221 and 231 for each feeder.Each feeder has an electric motor 213, 223, 233 which drives acorresponding feeding mechanism or feed screw 212, 222 and 232 (such asan auger or roller with pins) to propel fibrous material from a storagehopper to a desired location (i.e., the belt conveyor 205). Therespective motors are driven by an electrical signal received via outputlines 238 from feeder controller 236, the signal ranging from 0-100%motor speed.

[0039] As shown in FIG. 5, each feeder 210, 220 and 230 rests on acorresponding sensitive load cell 211, 221 and 231. These load cellsmeasure the weight of the feeder in small time increments (several timesper second) and sends a signal to feeder controller 236 via one of theinput lines 237 as the feeder is operating in the gravimetric mode. Thefeeder controller 236 calculates a feed rate over several of these timeincrements, and adaptively adjusts the motor speed of the feeder tocompensate by sending a signal via output lines 238 to the respectivemotors 213, 223 and 233. Thus, the average feed rate required to obtainthe desired ratio can be achieved over the operating period to conveyand mix materials for the resultant preform. Although in the preferredembodiment, a single feeder controller 236 preferably monitors allfeeders simultaneously during operation, each feeder can have its ownindividual feeder controller.

[0040] Once all parameters have been initialized, the operation proceedswith sequential deposition of chopped fibrous materials and resin bindermaterial onto conveyor belt 205 (Step S2). The layers are then mixed ina mixing step by material handling fan 240 (Step S3) and conveyed in anair volume to cyclone dust collector 260. There, the mixture of choppedfibrous material and resin binder is separated from the air volume anddeposited into the rotating mold 270 (Step S4). Once the mold is filledto a desired level, a drag chain conveyor (not shown in FIG. 2) isprovided to transport the mold of mixed materials to be consolidated.This provides a semi-continuous process of part fabrication, since thefeeders contain sufficient material to make many individual parts. Thus,when one “filled” mold is conveyed away from underneath cyclone dustcollector 260, another “empty” mold moves in and the filling cycle isrepeated.

[0041] Once a mold 270 is filled to a desired level and removed fromunderneath the cyclone dust collector 260, a consolidation process isperformed by heating the fiber and resin mixture, and subsequentlycompacting the ingredients in mold 270 to obtain an intermediatefiber-reinforced composite part of a desired shape (Step S5). Duringcompacting, the softened resin coats and impregnates the fibrousmaterial. After the mold is cooled below the resin softening point, theintermediate composite part or preform is ejected from the mold andsubjected to follow-on heating and densification treatments so as toobtain a final, fully-densified composite part (Step S6).

[0042] FIGS. 6-10 illustrate the steps of FIG. 4 in more detail. In FIG.6, Steps S11-S14 correspond to Step S2 of FIG. 4. In FIG. 7, StepsS15-S17 correspond to Step S3 of FIG. 4. In FIG. 8, Steps S18-S20correspond to Step S4 of FIG. 4. In FIG. 9, Steps S21 and S22 correspondto Step S5 in the process outlined in FIG. 4; and in FIG. 10, StepsS23-S28 correspond to Step S6 of FIG. 4.

[0043] Referring to FIG. 6, once all parameters have been initialized(completion of Step S1 in FIG. 4), the operation begins with the firstfeeder 210 gravimetrically depositing the reinforcing fibers at a firstpredetermined rate onto belt conveyor 205 (Step S11). The milled fibersand resin binder material from feeders 220 and 230 each have a staggeredstart such that the milled fiber chop and resin binder materials aresuccessively and gravimetrically deposited on top of the reinforcingfiber chop as the conveyor belt 205 passes underneath (Steps S12-S13).This forms a continuous tri-layer of materials (or more or less layers)on conveyor belt 205, which is subsequently dispensed into a materialhandling fan 240 (Step S14).

[0044] Referring to FIG. 7, the mixing step S3 carried out by materialhandling fan 240 has several purposes: it provides the air flow whichwill convey the combination of fibrous chop and resin binder material tothe mold 270. More importantly, it mixes together the layered materials(Step S15) while simultaneously defibrillating the reinforcing andmilled fibrous chop materials into smaller fiber strands (Steps S16).The defibrillation step further breaks up the reinforcing fibers andmilled fibers into smaller strands to promote even better mixing withthe resin binder material in material handling fan 240.

[0045] The use of material handling fan 240 allows control over theamount of desired defibrillation. Particularly, and unlike conventionalliquid slurry processes for example, where defibrillation is complete inbreaking up a fiber tow into individual filaments, material handling fan240 allows for a wide range of defibrillation, breaking up the choppedfibrous material into smaller filament bundles ranging from hundreds offilaments to almost 10,000 filaments, thereby preserving strength whileproviding improved wear properties for the resultant finished compositepart. The amount of defibrillation is governed by the material handlingfan speed. Keeping in mind that a minimum amount of air volume andvelocity is required to convey the materials (i.e. 50% maximum speed), alower fan speed provides less defibrillation. After mixing anddefibrillation, the “mixed materials” are conveyed via line 245 to acyclone dust collector 260 (Step S17).

[0046] Referring to FIG. 8, the cyclone dust collector 260 acts as aseparator, in conjunction with a return air fan 250. Specifically, the“fluid” entering cyclone dust collector 260 is a mix of thedefibrillated fibrous chopped materials and resin binder materialsentrained in a bulk volume of air. The return air fan 250 acts as avacuum to circulate the bulk of this air volume back to the materialhandling fan 240 via a line 255. This air removal process allows themixed materials to gently exit the bottom of the cyclone dust collector260 so that they are deposited into the rotating mold 270 (Step S18).

[0047] To further promote uniform dispersion of the mixed materials into the mold 270, the mold is rotated during deposition by turntable 272(Step S19). As the mold fills with the mixed materials, a dust filterfan 285 simultaneously creates a suction on mold 270 that removes anyentrained dust that is present when the mixed materials fill the mold270 (Step S20).

[0048] Referring to FIG. 9, once the mold 270 is filled to a desiredlevel, it is placed in an oven and heated to a temperature sufficient tosoften and/or melt the resin binder material, preferably at about 300°C. and 1 ATM (Step S21). After heating is completed, the mixed materialis compacted using a suitable method such as a hydraulic press, forexample, to impregnate the fiber tows and to obtain the desired finalshape of the intermediate composite part/preform (Step 22).

[0049] Referring to FIG. 10, the preform is cooled in the mold 270 untilthe resin binder material solidifies, and is then ejected from the mold270. (Step S23). The preform then undergoes oxygen stabilization (StepS24) whereby it is heated in circulating air (preferably about 170° C.)for an extended period. Alternatively, this step could be performed in acyclic pressure device (sometimes called an iron lung), by thermallyshocking the preform to develop cracks, or by subjecting the preform toa high pressure oxygen treatment at about 40 psi. Following oxygenstabilization, the preform is subjected to carbonization, where it isslowly heated (preferably between 1°/min to 1°/hr) to about 600-900° C.in nitrogen at atmospheric pressure (Step S25). Following carbonization,the preform undergoes a chemical vapor deposition (CVD)/chemical vaporinfiltration (CVI) process for up to about 600 hours to achieve fulldensity (Step S26). CVD/CVI includes approximately 50-200 hours ofCVD/CVI infiltration followed by at least 400 hours or more of CVD/CVIcycles, or densification can be performed by resin transfer molding(RTM) cycles, to fully densify the preform. A final heat treat isperformed in a standard temperature range of 1600-2200° C. thereafter toobtain a near final (machining is also typically required)fiber-reinforced composite part such as a carbon-carbon compositeaircraft brake disc (Step S27).

EXAMPLE

[0050] Several test parts were fabricated using the above method andapparatus, specifically nine (9) stator and six (6) rotor-size parts for767 aircraft made by the BOEING Corporation. For a stator, 3.976 pounds(1807 g) of 1-inch (2.54 cm) chop length carbon fiber (grade X9755) and1.454 pounds (661 g) of milled carbon fiber (grade 341, each grade offibers marketed by FORTAFIL), and 7.176 pounds (3262 g) of AR mesophasepitch resin (pellets ground into powder) marketed by the MITSUBISHI GasChemical Corporation were dispensed onto a belt conveyer overapproximately a thirteen (13) minute period (a total of 12.606 pounds or5723 g of “mixed material” was deposited in the mold over the timeperiod to form a preform). The material handling fan was operating at80% of the maximum motor speed, the return air fan at 37% of maximummotor speed and dust collector fan at 60% of maximum motor speed. Themold was located at a 2.5 inch (6.35 cm) linear position from thecenterline of the cyclone dust collector and was turning 6 rpm duringdeposition.

[0051] For this example, the stator part was built up in two equalbatches, due only to the current limitation of the 1-inch chopped fiberfeeder's hopper capacity. After the fibrous and binder materials weremixed and dispensed in the mold, the mold was placed into an aircirculating oven and heated to a temperature of 315° C. for four hours.After heating, the preform was compacted with 30 tons of force untilmechanical stops were met. The preform thickness was maintained at1.405″ (3.569 cm) until cool, and then was removed from the mold. Thedensity of the 5490 g weight preform was measured at 1.35 g/cc.

[0052] Therefore the method and apparatus in accordance with thepreferred embodiment enables the production of fiber-reinforcedcomposite parts suitable for use in manufacturing various high-frictioncomponents for applications such as automobile, truck, and aircraftbrakes. The density of the envisioned composite parts are between 1.2and 1.5 g/cc. By combining low-cost chopped PAN-based carbon fibers witha high carbon yielding mesophase pitch matrix resin, a carbon/carboncomposite material with improved friction and wear performance can beproduced in fewer processing steps as compared to current techniquesused to fabricate fiber-reinforced composite materials, therebyproviding increased reliability and reduced process cycle times. Suchfriction materials would typically have a density of at least 1.7 g/cc.

[0053] The invention being thus described, it will be obvious that thesame may be varied in many ways. For example, the constituent transportarrangement below feeders 210, 220 and 230 of FIG. 2 may be a pluralityof belt conveyors, each feeder having their own designated belt conveyerto transport the respective materials to a common mixing point. Inanother embodiment, a fourth feeder may be added to the apparatus inFIG. 2 to deposit other performance modifying additives which might benecessary in forming the resultant composite part. These additives caninclude materials such as metals, ceramic particles, graphite, cokes,curing agents, mica, carbon oxidation inhibitors, glass or polymerfilms, or any other agents or materials which improve friction and wearcharacteristics of a composite part and/or to further strengthen thefibrous/binder materials used to fabricate the composite part.Alternatively, these additives may be mixed in with the resin bindermaterial at feeder 230 to conserve space.

[0054] Additionally, in lieu of or in addition to performing oxygenstabilization (Step 24) of the intermediate part (FIG. 9), a support orconstraint fixture may be utilized during carbonization (Step S25) toprevent bloating and maintain part shape. Further regarding FIG. 9, anoptional heat treat (HTT—High Temperature Treatment) may be performedbetween carbonization (Step S25) and CVD/CVI (Step S26), heating thepreform at about 1°/min to about 1800° C. Such variations are not to beregarded as a departure from the spirit and scope of the invention, andall such modifications as would be obvious to one skilled in the art,are intended to be included within the scope of the following claims.

What is claimed is:
 1. An apparatus for forming fiber reinforcedcomposite parts, comprising: a plurality of feeder mechanisms fordepositing fibrous materials and a resin material on a constituenttransport arrangement so that said resin material and said fibrousmaterials are in a predetermined ratio; a mixer for mixing said fibrousand resin materials received from said constituent transportarrangement, and a conveyance medium for depositing said mixed materialsin a mold of desired shape.
 2. The apparatus of claim 1, wherein saidconstituent transport arrangement is a single belt conveyor whichreceives a continuous stacked layer of fibrous and binder materials. 3.The apparatus of claim 1, wherein said plurality of feeder mechanismsgravimetrically feed said fibrous and binder materials at specifiedrates onto said belt conveyer to obtain said predetermined ratio.
 4. Theapparatus of claim 1, wherein said fibrous materials include chopped ormilled carbon fibers of various lengths, and wherein said bindermaterial includes a powdered matrix resin binder.
 5. The apparatus ofclaim 1, wherein said fibrous materials include chopped or milled carbonfibers up to about 1.5 inches in length.
 6. The apparatus of claim 1,wherein said fibrous materials include first and second portions ofchopped or milled carbon fibers of various lengths, said first portionof carbon fiber greater in length than said second portion.
 7. Theapparatus of claim 1, further comprising a collector for collecting saidmixed materials, wherein said mixer includes a first fan for mixing saidfibrous and binder materials, and wherein said conveyance medium is anairflow volume provided by said first fan to convey said mixed materialsto said collector.
 8. The apparatus of claim 7, wherein said collectorincludes a second fan which circulates substantially all of said airflowvolume back to said first fan so that said mixed materials are separatedtherefrom in said collector, exiting a bottom of the collector toaccumulate in said mold.
 9. The apparatus of claim 1, wherein saidconstituent transport arrangement includes a plurality of conveyors,each associated with a corresponding feeder to convey layers of fibrousand binder materials separately from each other to be combined at saidmixer.
 10. The apparatus of claim 1, wherein said mold rotates whilereceiving said mixed materials to provide uniform dispersion of fibrousand binder materials therein.
 11. The apparatus of claim 1, furtherincluding a rotational device which supports said mold, wherein saidrotational device imparts rotational and linear motion to said moldduring deposition of said mixed materials to provide uniform dispersionof fibrous and binder materials within said mold.
 12. The apparatus ofclaim 1, wherein said mold is heated without curing and compacted toform an intermediate composite part, and wherein said intermediatecomposite part is thereafter subjected to a follow-on heating anddensification process to obtain a fully-densified fiber-reinforcedcomposite part.
 13. The apparatus of claim 1, wherein one of saidplurality of feeders deposits said resin material mixed with performancemodifying additives on said constituent transport arrangement.
 14. Theapparatus of claim 1, wherein one of said plurality of feeders depositsperformance modifying additives on said constituent transportarrangement.
 15. An apparatus for forming fiber-reinforced compositeparts, comprising: a plurality of feeder mechanisms for depositing aportion of chopped or milled carbon fibers and a portion of powderedmatrix resin binder in predetermined ratios onto a constituent transportarrangement; a mixer for mixing said carbon fiber and said powderedmatrix resin binder portions to form mixed materials; and a mold forreceiving said mixed materials from said mixer, wherein said mixedmaterials are substantially uniformly dispersed in said mold so thatsubsequent heating of said mold enables in-situ impregnation of saidcarbon fiber portions with said powdered matrix resin binder portions.16. The apparatus of claim 15, wherein said portions are successivelylayered on top of each other in a predetermined ratio
 17. A method offorming fiber reinforced composite parts, comprising: feeding separatefibrous and binder materials onto a constituent transport arrangement ina predetermined ratio of materials; mixing said fibrous and bindermaterials to form mixed materials; depositing said mixed materials in amold of desired shape; heating said mixed materials in said mold; andcompacting said mixed materials in said mold to obtain a desired shape.18. The method of claim 17, wherein each of said materials aresuccessively layered on, top of each other in a predetermined ratio. 19.The method of claim 17, wherein said feeding includes gravimetricallyfeeding each of said fibrous and binder materials at specified ratesonto said belt conveyer to obtain said predetermined ratio.
 20. Themethod of claim 19, wherein said specified rates are adaptivelycontrolled.
 21. The method of claim 17, wherein said fibrous materialsinclude first and second portions of chopped or milled carbon fibers ofvarious lengths; and wherein said binder material includes a powderedmatrix resin binder.
 22. The method of claim 17, wherein said fibrousmaterials include chopped or milled carbon fibers up to about 1.5 inchesin length.
 23. The method of claim 17, wherein said fibrous materialsinclude first and second carbon fiber portions of various lengths, saidfirst carbon fiber portion being greater in length than said secondcarbon fiber portion.
 24. The method of claim 17, wherein said step ofmixing provides airflow to convey said mixed materials to said mold,said airflow being separated from said mixed materials at said mold sothat substantially only said mixed materials are deposited into saidmold.
 25. The method of claim 17, wherein said heating further includesin-situ impregnating said fibrous material with said binder materialwithin said mold.
 26. The method of claim 17, wherein said compactingfurther includes hydraulically pressing said mixed materials in saidmold after heating, whereupon said mold is cooled to provide a finishedfiber-reinforced composite part.
 27. The method of claim 17, whereinsaid depositing further includes rotating said mold while receiving saidmixed materials to provide uniform dispersion of fibrous and bindermaterials therein.
 28. The method of claim 27, wherein said rotatingincludes linearly displacing said mold during deposition of said mixedmaterials to provide uniform dispersion of fibrous and binder materialstherein.
 29. The method of claim 17, wherein said shape forms anintermediate composite part which is thereafter subjected to a series offollow-on heating and densification processes to obtain afully-densified fiber-reinforced composite part.
 30. The method of claim29, wherein said composite part is a final, fully-densifiedcarbon-carbon composite part.
 31. The method of claim 29, wherein saidcomposite part is an aircraft brake disc.
 32. The method of claim 17,wherein said feeding further includes feeding performance modifyingadditives onto said constituent transport arrangement.
 33. The method ofclaim 17, wherein said feeding further includes feeding said bindermixed with performance modifying additives onto said constituenttransport arrangement.
 34. A method of forming fiber reinforcedcomposite parts, comprising: feeding portions of chopped or milledcarbon fibers and a portion of powdered matrix resin binder onto aconstituent transport arrangement in a predetermined ratio; mixing saidcarbon fiber and matrix resin portions to form mixed materials; anddepositing said mixed materials in a mold of desired shape, wherein saidmold is rotated and linearly displaced during deposition to provideuniform dispersion of fibrous and binder materials therein.
 35. Themethod of claim 34, wherein said carbon fiber portions and said resinportion are successively layered on top of each other in a predeterminedratio.
 36. The method of claim 34, further comprising: heating saidmixed materials within said mold and compacting said heated materials toimpregnate the fiber portions with said resin binder and obtain adesired final shape.
 37. A rotation device used in forming fiberreinforced composite parts, comprising: a turntable for rotating a moldthereon; and an actuator for supporting said turntable, and forproviding reciprocating motion to said mold, wherein said turntable andactuator simultaneously rotate and reciprocate said mold during adeposition of mixed fibrous and binder materials therein to providesubstantially uniform dispersion of fibrous and binder materials,thereby improving densification of the final formed composite part. 38.A fiber-reinforced composite part comprising fibrous material combinedwith a dry resin material in predetermined ratios that are mixed andconveyed as mixed material to a mold of desired shape, and subsequentlyheated and compacted to obtain a shaped part having a density in therange of 1.2 to 1.5 g/cc.
 39. The composite part of claim 38, whereinthe composite part is a carbon-carbon composite.
 40. The composite partof claim 38, wherein after carbonization the part is a porous composite.41. A fiber reinforced composite part comprising a shaped preform formedby combining a fibrous material with a dry resin material inpredetermined ratios which are mixed and conveyed as mixed material to amold of desired shape and subsequently heated and compacted, the shapedpreform thereafter subject to a plurality of follow-on heating anddensification processes to obtain the fully-densified part having adensity of at least 1.7 g/cc.
 42. The composite part of claim 41,wherein the part is an aircraft brake disc.